History of GPS – Part I
Today Global Positioning System technologies have become integrated into our daily lives, whether we know it or not. Dozens of new gadgets flood the market each month boasting GPS capability; they come embedded in cars, boats, airplanes, construction machinery, farm equipment, even your mobile phone and laptop computer. Its functions are simple and necessary: navigation, tracking, surveying, timing – the same basic tasks conducted by civilizations for centuries, only now they have become immensely faster, easier and more precise than ever. As the technology becomes more and more a part of the fabric of our routines, it is easy to overlook the spectacular journey GPS has made from its breeding ground in military applications to today’s high-tech consumer toys.
The infrastructure supporting GPS technology is surprisingly simple, yet also technically complex in its precision and ingenuity. Since 1994, all GPS capabilities have been supported by a constellation of at least 24 satellites, each measuring about 17 feet across and weighing approximately one ton, that are part of a global navigation satellite system. Powered primarily by solar energy, they circle the earth at an altitude of more than 12,000 miles and speeds of around 7,000 miles an hour, completing two orbits in less than 24 hours. The satellites emit microwaves that allow GPS receivers to determine their exact location, speed, direction, and time through triangulation of the signals. Officially named NAVSTAR, the GPS constellation took the government more than $12 billion to build and costs roughly $750 million a year to maintain, a price tag that includes satellite replacement and research and development. In the last decade, the number of actively broadcasting satellites has grown from 24 to 31, arranged in a nonuniform pattern, which provides redundant measurements and improve reliability and availability of the system.
The GPS satellite constellation in use today was first achieved in 1994, but groundwork for such a system began much earlier. GPS technology was built upon principles of radionavigation, which was used as early as the 1920s by mariners utilizing land-based transmitters to find shore. During the World War II era, the Massachusetts Institute of Technology Radiation Laboratory developed a radionavigation system known as LORAN (Long Range Aid to Navigation), the first of its kind to use difference-of-arrival radio signals for all-weather navigation purposes, a forerunner for GPS technology.
It wasn’t until the late 1950s and early 1960s that the idea picked up steam with a series of breakthroughs. In 1957, the Soviet Union launched the first Sputnik, which was closely monitored by a team of U.S. scientists. While tracking the radio signals, they discovered they could pinpoint the exact position of the satellite based on frequency because of Doppler distortion.
Also at the time, the global arms race was heating up, and the importance for an accurate, all-weather, continuously available positioning system became increasingly apparent. With advances made in intercontinental ballistic missiles, the U.S. needed a way to precisely fix its nuclear arsenal onto targets around the world from its fleet of submarines and a guidance system for missiles traveling on a railroad system.
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Tags: GPS Tracking, History of GPS, LORAN, NAVSTAR, Richard Kirschner, Roger Easton
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April 30th, 2010 at 8:53 am
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